Surface-Enhanced Raman Scattering of dopamine adsorbed on TiO2 films

NICOLÁS A. RODRÍGUEZ; RODRIGO PARRA; M. ALEJANDRA GRELA

Florianópolis

Congreso; XI Encuentro de la SBP Mat; 2012

The surface-enhanced Raman scattering (SERS) is a promising technique for the analysis of species at very low concentrations. Compared with conventional Raman analysis, signal enhancements in excess of a million times have been reported for roughened metal surfaces. Frequently, noble metals and some transition metals are employed as substrates for SERS. However, the SERS effect has also been detected for some organic molecules adsorbed at TiO2 nanoparticles [1], and complexes between TiO2 and enediols have been modelled and characterized [2]. The aim of this work is to study the use TiO2 films as substrates for SERS to take reproducible measurements of samples containing dopamine. In the present work, TiO2 porous films of thicknesses between 1 and 10 µm were prepared by a doctor blade technique from TiO2 aqueous dispersions(5-20%wt.)obtained by hydrothermal synthesis from titanium isopropoxide. Films were heat-treated at 450ºC for the burning of organics and sintering. Thickness, particle size and porosity were analysed with the aid of X-Ray Diffraction and Scanning Electron Microscopy. Sintered films were soaked in dopamine solutions of different concentrations in order to study the SERS effect. The formation of a charge transfer complex between the target analyte and TiO2 could be confirmed by EPR and UV-Vis spectroscopies. The influence of film thickness and dopamine concentration were discussed based on the dopamine Raman signal at 1489cm-1. Additionally, these results are compared with the Raman signal of dopamine in the absence of the semiconductor layer. Keywords: SERS, TiO2 thin films, dopamine. [1] L. Yang, X. Jiang; W. Ruan, B. Zhao, W. Xu, J.R. Lombardi. ?Observation of Enhanced Raman Scattering for Molecules Adsorbed on TiO2 Nanoparticles: Charge-Transfer Contribution?. J. Phys. Chem. C, 112 (2008) 20095. [2] P. Tarakeshwar, D. Finkelstein-Shapiro, S. J. Hurst, T. Rajh, and V. Mujica ?Surface- Enhanced Raman Scattering on Semiconducting Oxide Nanoparticles: Oxide Nature, Size, Solvent, and pH Effects? J. Phys. Chem. C, 115 (2011) 8994.